An ultrahigh-voltage (UHV) semiconductor device, which can sustain a higher voltage operation, is one of the most important devices utilized in modern integrated circuits. Generally, the higher voltage operation refers to an application of an UHV input (>100V) from an external source to an UHV device.
A common UHV semiconductor device usually includes high voltage circuits and low voltage circuits integrated into a single chip. In which, the high-voltage circuits are composed of an UHV semiconductor structure. The UHV semiconductor structure includes a P-type semiconductor substrate, an N-type semiconductor well in the P-type semiconductor substrate, a P-type semiconductor well in the N-type semiconductor well, and an anode on the P-type semiconductor well. Further, the P-type semiconductor substrate, the N-type semiconductor well and the P-type semiconductor well form a PNP bipolar structure.
However, during forward operation of a semiconductor diode, the UHV semiconductor structure has current leakage from a parasitic PNP bipolar structure. When the current leakage occurs at UHV operation, the current may flow from the anode to the P-type semiconductor substrate and damage the UHV semiconductor device causing electrical failure thereof. Accordingly, improvements in structures and methods for fabricating the UHV semiconductor device continue to be sought.